support, and AD was liquidated on 8 June. Airship Developments, 1979–80 Following the loss of the AD500 prototype, the Aerospace Developments design team was reconstituted in September 1979 under the name Airship Developments Limited. During its short period under this name, the firm projected five non-rigid airship designs (several of which echoed the earlier AD proposals): AD15: a remotely piloted surveillance vehicle with a gas capacity of AD100: a "runabout blimp" with of gas AD500: a rebuilt version of the prototype AD600: an enlarged AD500 with a gas capacity of (i.e. around 10% less than the eventual Skyship 600) AD5000: an extremely large (by non-rigid standards) craft with of gas and a payload of over , foreshadowing the later Sentinel 5000/YEZ-2A programme Airship Industries, 1980–90 Thermo-Skyships takeover In May 1980, Airship Developments was acquired by Thermo-Skyships Ltd., a firm that had been working on lenticular airship designs (dubbed "flying saucers") that would have used heating of the lifting gas to control buoyancy. The resulting firm was known as Airship Industries Ltd.(AI). During the approximately two-and-a-half years the Thermo-Skyships team spent at AI, it proposed several abortive designs, for non-lenticular rigid airships. Skyship 500 The AD500 was succeeded by the Skyship 500 model. The first flight of a Skyship 500 proper (i.e. excluding the AD500) took place from Cardington on 28 September 1981. The ship incorporated "many detail improvements" relative to the AD500, including a new envelope material, improved actuators, and an overall weight saving of around . Five more 500s were subsequently built — one at Cardington, two in Toronto, one in Tokyo, and one in the United States. The ships were mainly used in advertising and filming. Other uses of the craft included sightseeing flights over London, a trial shuttle service between Paris's Orly and Charles de Gaulle airports and trials with NASA and the United States Air Force, United States Navy and United States Coast Guard. Four 500s were later upgraded to 500HL standards by mating the 500 gondola to a 600 envelope in order to increase lift for heavy payloads or hot and high applications. Two more 500 gondolas were begun but never completed. Proposed rigid airships—R40/R130 and R150 The former Thermo-Skyships design team proposed two rigid designs during their time with AI. In July 1980, AI announced "ambitious plans" to begin construction of a freight-carrying rigid, designated the Skyship R40, in early 1982. The airship (which